我正在使用这段代码在docker容器中使用
python pcapy:
from pcapy import open_live, findalldevs
import sys
import traceback
p = open_live("eth0", 1024, False, 100)
dumper = p.dump_open("test.pcap")
devices = findalldevs()
print dumper, devices
while True:
try:
print p.next()
except Exception as e:
print dir(e), e.message, e.args[0]
traceback.print_exc(file=sys.stdout)
break
当我运行它时,我得到以下异常:
Traceback (most recent call last):
File “test_pcap.py”, line 12, in
06001
PcapError
我试图通过更改为不同的最大数据包大小并将混杂设置为True来使用参数.
我试图从异常中获取任何消息,但似乎消息是空的.我还浏览了pcapy source code:由于PcapyError对象中的异常是空的,而下一个函数中的其他PcapErrors是显式字符串,这意味着我们正陷入buf为空的状态.似乎pcap_geterr返回一个空字符串,因为pp-> pcap已经关闭,并且指向pcap异常的指针不再存在(请查看doc).
当我使用loop()方法运行时,一切正常:
# Modified from: http://snipplr.com/view/3579/
import pcapy
from impacket.ImpactDecoder import *
# list all the network devices
pcapy.findalldevs()
max_bytes = 1024
promiscuous = False
read_timeout = 100 # in milliseconds
pc = pcapy.open_live("eth0", max_bytes,
promiscuous, read_timeout)
# callback for received packets
def recv_pkts(hdr, data):
packet = EthDecoder().decode(data)
print packet
packet_limit = -1 # infinite
pc.loop(packet_limit, recv_pkts) # capture packets
我真的不知道问题的根源或者为调试它做了什么.
编辑
我使用strace找不到任何错误.这是strace输出中的错误的grep:
strace python test_pcap.py 2>&1 1>/dev/null | grep -i error
read(6, “\0\0\0t\3\0\0\0intt\n\0\0\0ValueErrort\23\0\0\0_”…, 4096) = 995
getsockopt(3, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
getsockopt(5, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
getsockopt(5, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
EDIT2
我也通过自己调用pcap_next来测试pcap.h:
// Modified from: http://www.tcpdump.org/pcap.html
#include <pcap.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
pcap_t *handle; /* Session handle */
char *dev; /* The device to sniff on */
char errbuf[PCAP_ERRBUF_SIZE]; /* Error string */
bpf_u_int32 mask; /* Our netmask */
bpf_u_int32 net; /* Our IP */
struct pcap_pkthdr header; /* The header that pcap gives us */
const u_char *packet; /* The actual packet */
/* Define the device */
dev = pcap_lookupdev(errbuf);
if (dev == NULL) {
fprintf(stderr, "Couldn't find default device: %s\n", errbuf);
return(2);
}
/* Find the properties for the device */
if (pcap_lookupnet(dev, &net, &mask, errbuf) == -1) {
fprintf(stderr, "Couldn't get netmask for device %s: %s\n", dev, errbuf);
net = 0;
mask = 0;
}
/* Open the session in promiscuous mode */
handle = pcap_open_live(dev, BUFSIZ, 1, 1000, errbuf);
if (handle == NULL) {
fprintf(stderr, "Couldn't open device %s: %s\n", "eth0", errbuf);
return(2);
}
while (1) {
/* Grab a packet */
packet = pcap_next(handle, &header);
/* Print its length */
printf("Jacked a packet with length of [%d]\n", header.len);
/* Print contents */
printf("\tPacket: %s\n", packet);
/* And close the session */
}
pcap_close(handle);
return(0);
}
要编译,请将其写入test_sniff.c并运行:
gcc test_sniff.c -o test_sniff -lpcap
我能够成功捕获数据包.所以我真的不知道问题出在哪里……
其他信息,以重现行为
> Docker版本:Docker版本1.5.0,构建a8a31ef
> Docker镜像是Docker默认的Ubuntu
> Python2.7
最佳答案 pcapy不使用Python套接字模块.如果先前的socket.settimeout调用启用了超时,则不会引发socket.timeout. socket.settimeout用于将套接字设置为阻塞,非阻塞或超时状态.
在pcapy中,open_live的超时参数至少在Linux中传递给poll syscall,因为不存在poll的操作系统会有所不同.
如果没有要返回的数据包,则Reader.next调用会引发PcapError,因为它尚未捕获任何数据包.这不是错误,只是像StopIteration这样的指示.它可以被忽略,并且必须再次调用Reader.next.
Reader.loop在返回至少一个数据包或发生错误之前不会返回.
以下代码捕获10个数据包并退出.
from pcapy import open_live, findalldevs, PcapError
p = open_live("eth0", 1024, False, 100)
dumper = p.dump_open("test.pcap")
devices = findalldevs()
print dumper, devices
count=0
while True:
try:
packet = p.next()
except PcapError:
continue
else:
print packet
count += 1
if count == 10:
break